Roots of plants play many functions in survival of a plant. Matured roots support the plant. Root hair absorbs water and water soluble minerals from the medium in which they grow. All living roots of a plant also respire; and that is why most plants need friable planting mixture, which allows aeration near the root zone. It is very interesting to know how roots of different plants get modified to survive in adverse conditions.
Adventitious roots: Some climbers like money plant and Betel leaf cling to support with 'Adventitious roots'. Unlike roots in soil, they grow on stems and cling to support for climbing up. Though their primary task is clinging to support, they are capable of absorbing moisture and water soluble minerals. Plumeria plants, which are succulent, quite often grow adventitious roots, particularly if they face water scarcity. These aerial roots are capable of trapping dewdrops and rain water.
Adventitious roots of Pandanus are called as 'Prop roots'. Pandanus plants quite often grow in sandy, marshy areas like creeks, sea shores etc. Compared to huge size of their leafy canopy, the stems are feeble. Also in sandy and slushy soil the normal roots cannot support these plants firmly. So to support the plant the trunks and side branches grow these prop roots, which act like crutches and thus support the plant firmly. Prop roots of Pandanus also have prominent root caps.
Prop roots of Ficus bengalensis (Banyan). Banyan tree have huge crown which goes on spreading in all directions. Wood of Banyan tree is quite brittle so to prevent the branches from breaking down due to their weight, Banyan tree grow prop roots on their branches. These prop roots enter the ground and firmly support the branches. In Acharya Jagadish Chandra Bose Botanica Garden, Kolkata, there is a huge Banyan tree which covers the area of 1.6 Hectares and has more than 3600 prop roots.
Spongy roots of epiphytic orchids: Epiphytic orchids have thick and spongy roots. These roots are capable of absorbing moisture from the air. Such epiphytic orchids if planted in soil get suffocated and rot; which could cause death of that orchid. In nature these orchids cling to support with their roots only. So these roots have dual purpose; clinging to support (normally on tree trunks in their natural surroundings) and also of absorbing water and water soluble minerals. For planting epiphytic orchids in pots, one must use charcoal, brickbats and coconut skin pieces. Alternately they can be mounted on dead wood covered with thin layer of sphagnum moss.
Pneumatophore roots of mangrove plants: Mangroves grow in marshy patches of creeks and estuaries. As most of the time their root system is under water, mangrove plants like Avicennia have special roots that emerge out of soil and water for respiration. These roots are called as Pneumatophore.
Roots of epiphytic Bromeliads: Epiphytic bromeliad plants have very thin and wiry roots. The primary function of these roots is to cling to support (mainly to tree trunks and rocks). These roots are almost sheltered by the large whorl of leaves. As such very little water in form of rain and dewdrops can reach the roots. So these epiphytic bromeliads collect water in the central vase-like cavity formed by the whorled leaves. Bases of the leaves, where they are attached to the stem are spongy. These specialized cell absorb water to keep these plants alive. If planted in pots, even if their root system is kept dry, one must replenish water in the vase formed by the leaves.
Buttress roots: Certain trees, like Gulmohur etc, have a root system which does not go deep in soil. So to support the trees firmly they start growing buttress roots. These hard, woody roots support the tree firmly on the ground. These roots quite often spread quite far growing horizontally. In certain tall trees they do not spread far but support the stem at higher points. A beautiful specimen of Kapok tree in Lalbaug Garden in Bengaluru is a classic example having very large buttress roots. In fact many couple use to hide in the gaps of these buttress roots to get intimate. Now the tree is barricaded with fencing to prevent these Laila Majnu.
Root tubers: Dahlia, Asparagus, Sweet potato etc. have swollen roots. These roots store excess food manufactured by the plant.
Haustorium: Parasitic plants have specialized roots called Haustorium. These roots penetrate the host plant to get food and water. Cuscuta is a climbing parasite. Intially it grows in soil. The moment it finds a host, its contact with soil is terminated. The stems of cuscuta send haustorium in to the host and deprive the host of its own food and water, often causing death of the host. A beautiful flowering parasite, Cistanche tubulosa, is a root parasite. Its roots penetrate the roots of the host plant Salvadora persica, commonly known as Mesvac plant.
Symbiosis in roots: Plants belonging to Fabaceae family have some nodules on their roots. These nodules harbor certain bacteria which absorb insoluble Nitrogen from air and convert it to water soluble form. Thus the plant roots shelter the bacteria and in return the bacteria provide with vital Nitrogen.
Adventitious roots: Some climbers like money plant and Betel leaf cling to support with 'Adventitious roots'. Unlike roots in soil, they grow on stems and cling to support for climbing up. Though their primary task is clinging to support, they are capable of absorbing moisture and water soluble minerals. Plumeria plants, which are succulent, quite often grow adventitious roots, particularly if they face water scarcity. These aerial roots are capable of trapping dewdrops and rain water.
Adventitious roots of Pandanus are called as 'Prop roots'. Pandanus plants quite often grow in sandy, marshy areas like creeks, sea shores etc. Compared to huge size of their leafy canopy, the stems are feeble. Also in sandy and slushy soil the normal roots cannot support these plants firmly. So to support the plant the trunks and side branches grow these prop roots, which act like crutches and thus support the plant firmly. Prop roots of Pandanus also have prominent root caps.
Prop roots of Ficus bengalensis (Banyan). Banyan tree have huge crown which goes on spreading in all directions. Wood of Banyan tree is quite brittle so to prevent the branches from breaking down due to their weight, Banyan tree grow prop roots on their branches. These prop roots enter the ground and firmly support the branches. In Acharya Jagadish Chandra Bose Botanica Garden, Kolkata, there is a huge Banyan tree which covers the area of 1.6 Hectares and has more than 3600 prop roots.
Spongy roots of epiphytic orchids: Epiphytic orchids have thick and spongy roots. These roots are capable of absorbing moisture from the air. Such epiphytic orchids if planted in soil get suffocated and rot; which could cause death of that orchid. In nature these orchids cling to support with their roots only. So these roots have dual purpose; clinging to support (normally on tree trunks in their natural surroundings) and also of absorbing water and water soluble minerals. For planting epiphytic orchids in pots, one must use charcoal, brickbats and coconut skin pieces. Alternately they can be mounted on dead wood covered with thin layer of sphagnum moss.
Roots of epiphytic Bromeliads: Epiphytic bromeliad plants have very thin and wiry roots. The primary function of these roots is to cling to support (mainly to tree trunks and rocks). These roots are almost sheltered by the large whorl of leaves. As such very little water in form of rain and dewdrops can reach the roots. So these epiphytic bromeliads collect water in the central vase-like cavity formed by the whorled leaves. Bases of the leaves, where they are attached to the stem are spongy. These specialized cell absorb water to keep these plants alive. If planted in pots, even if their root system is kept dry, one must replenish water in the vase formed by the leaves.
Buttress roots: Certain trees, like Gulmohur etc, have a root system which does not go deep in soil. So to support the trees firmly they start growing buttress roots. These hard, woody roots support the tree firmly on the ground. These roots quite often spread quite far growing horizontally. In certain tall trees they do not spread far but support the stem at higher points. A beautiful specimen of Kapok tree in Lalbaug Garden in Bengaluru is a classic example having very large buttress roots. In fact many couple use to hide in the gaps of these buttress roots to get intimate. Now the tree is barricaded with fencing to prevent these Laila Majnu.
Root tubers: Dahlia, Asparagus, Sweet potato etc. have swollen roots. These roots store excess food manufactured by the plant.
Haustorium: Parasitic plants have specialized roots called Haustorium. These roots penetrate the host plant to get food and water. Cuscuta is a climbing parasite. Intially it grows in soil. The moment it finds a host, its contact with soil is terminated. The stems of cuscuta send haustorium in to the host and deprive the host of its own food and water, often causing death of the host. A beautiful flowering parasite, Cistanche tubulosa, is a root parasite. Its roots penetrate the roots of the host plant Salvadora persica, commonly known as Mesvac plant.
Symbiosis in roots: Plants belonging to Fabaceae family have some nodules on their roots. These nodules harbor certain bacteria which absorb insoluble Nitrogen from air and convert it to water soluble form. Thus the plant roots shelter the bacteria and in return the bacteria provide with vital Nitrogen.
